If 
, show that 
.
Given 
LHS 
We know that sin(A ±B) = sinA cosB ± cosA sinB And cos(A ±B) = cosA cosB ∓ sinA sinB
= tanA = RHS
19
If , show that .
Given
LHS
We know that sin(A ±B) = sinA cosB ± cosA sinB And cos(A ±B) = cosA cosB ∓ sinA sinB
= tanA = RHS